The field of invention relates generally to support for substrates. More particularly, the present invention is directed to a chuck suited for use in imprint lithography.
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like. Many of the micro-fabrication techniques involve various processes, including deposition, such as chemical vapor deposition, physical vapor deposition, atomic layer deposition and the like, as well as wet and/or dry etching techniques to pattern substrates.
In addition to the standard micro-fabrication techniques, there exists a relatively new and efficient patterning technique referred to as imprint lithography. An exemplary imprint lithography is described in detail in numerous publications, such as U.S. Pat. No. 6,873,087 entitled HIGH PRECISION ORIENTATION ALIGNMENT AND GAP CONTROL STAGES FOR IMPRINT LITHOGRAPHY PROCESSES; U.S. Pat. No. 6,842,226, entitled IMPRINT LITHOGRAPHY TEMPLATE COMPRISING ALIGNMENT MARKS; U.S. Pat. No. 6,696,220 entitled TEMPLATE FOR ROOM TEMPERATURE, LOW PRESSURE MICRO-AND NANO-IMPRINT LITHOGRAPHY; and U.S. Pat. No. 6,719,915 entitled STEP AND FLASH IMPRINT LITHOGRAPHY, all of which are assigned to the assignee of the present invention. The fundamental imprint lithography technique as shown in each of the aforementioned published patent applications includes formatting a relief pattern in a polymerizable layer and transferring the relief pattern into an underlying substrate to form a relief image in the substrate. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified forming a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The substrate and the solidified layer are then subjected to processes to transfer into the substrate a relief image that corresponds to the pattern in the solidified layer.
As a result of the aforementioned micro-fabrication techniques, the demand to ensure the flatness/planarity of substrates being processed/patterned has increased, because of the decreasing size of the features being formed. There are a number of factors affecting substrate planarity, many of which can be corrected by conventional substrate chucks. However, the presence of backside particles, particles that contact a surface of a substrate opposite to the surface being patterned, are problematic. For example, particles may become lodged between the substrate and the chuck, referred to as backside particles, which may cause out-of-plane distortion of the substrate resulting in distortions in the pattern generated on the substrate. Out-of-plane distortions may be characterized as possessing two parameters: 1) distortion height; and 2) gap radius. The distortion height is defined as the maximum out-of-plane deviation produced in the substrate by the backside particle. Gap radius is defined as a measure of the length of a region of the substrate spaced-apart from the chuck, measured between the particle and a point of the substrate closest to the particle at which the substrate contacts the chuck. It can be realized that the area of a substrate that undergoes distortion due to the presence of particulate contaminants is much greater than the size of the particulates.
Prior art attempts to overcome particulate contaminants include pin type and groove type chucks. These chucking systems attempt to avoid the drawbacks associated with backside particles by minimizing the contact area between the substrate and the chuck. However, these chucking systems only reduce the probability of particles being lodged between the chuck and the substrate, but do not avoid or attenuate the non-planarity should a particle get lodged between a chuck and a substrate.
There is a need, therefore, to provide improved support systems for substrates.